The α-Fe2O3 is an abundant, safe and low-cost anode material, but it has not been widely used due to its poor electrical conductivity and large volume expansion. In this work, in order to improve the ...electrical conductivity of α-Fe2O3, the Co-α-Fe2O3/Graphene composites with different Co-doping concentrations were prepared by the solvothermal method. After doping Co into the α-Fe2O3 crystal, the interlayer spacing of the cell is increased, and the diffusion channel of Li+ is enlarged. The average grain size of α-Fe2O3 decreases gradually as well. At the same time, oxygen vacancies were introduced, which significantly improved the electrical properties of α-Fe2O3, and the band gap width of α-Fe2O3 was reduced from 2.04 eV to 1.89 eV. Besides, the introduction of graphene not only make the electrical conductivity of the composite better, but also alleviates the volume expansion of the metal oxide during cycling. The Co-α-Fe2O3/Graphene composite shows excellent electrochemical properties as the anode material for the LIBs. When the doping amount is 5%, the reversible capacity of the composite electrode could reach 886 mAh/g at 1 C after 200 cycles, showing good cycling stability and rate performance. The results indicate that the synergistic effect of doping Co and graphene greatly improves the electrochemical performance of Co-α-Fe2O3/Graphene composites.
Display omitted
A wide range of heat transfer systems require efficient heat transfer management from source to sink and vice versa. Over the last decade, graphene nanoparticles, matrix nanofluids have been one of ...the most investigated nanoparticles for a wide range of engineering applications. Graphene–based nanoparticles have several advantages over other nanoparticles: high stability, high thermal conductivity, low erosion and corrosion, and higher carrier mobility. Graphene–based nanofluids have found applications such as heat transfer, defect sensor, anti–infection therapy, energy harvesting systems, biomedical and cosmetics. With advancement of technology, more compact and efficient cooling media are needed to ensure efficiency and reliability of engineering systems and devices. This research study reports an overview of experimental and numerical investigations of graphene nanometer–sized particles with different base host fluids for major engineering applications of energy transfer systems and further thermophysical properties of graphene nanofluids.
•Various synthesis and preparation methods of graphene oxide are discussed in detail.•Preparation methods of graphene nanofluids with different base fluids are summarized in detail using different techniques.•Stability evaluation, enhancement and mechanism methods of graphene nanofluid are described thoroughly.•Effective parameters which influence the thermal properties are discussed.•The applications of graphene based nanofluid in major heat transfer systems are detailed summarized.
•Thermophysical properties of graphene dispersed erythritol PCM (NDPCM) analysed.•FTIR spectrum confirmed graphene nanoparticles integrated well into erythritol PCM.•DSC results revealed less change ...in latent heat and phase change temperature after 100 thermal cycles.•1 wt. % graphene increases thermal conductivity by 53.1% with only 6.1% decrease in latent heat of erythritol.•Addition of graphene has a positive influence, i.e. the degree of subcooling is reduced.
Nanoparticles dispersed phase change material (NDPCM) is a new kind of PCM developed by suspending nano-size particles in base PCM for the main purpose of enhancing the thermo-physical properties of the base PCM. In the present research work, the feasibility and thermal conductivity enhancement of dispersing graphene particles in three different mass fractions (0.1%, 0.5% and 1%) into the erythritol base PCM were examined. The FTIR spectrum showed that the graphene nanoparticles integrated well into erythritol PCM without affecting its chemical properties. The DSC results revealed that the change in latent heat and phase change temperature of NDPCM is less before and after 100 melting and solidification cycles. Addition of 1 wt. % graphene led to 53.1% increase in thermal conductivity with only 6.1% decrease in latent heat enthalpy. Also, there was a 5.8% decrease in melting temperature and 18.76% increase in solidification temperature relative to pure erythritol.
Display omitted
To prepare a high-performance catalyst for heterogeneous catalytic ozonation (HCO) of atrazine (ATZ, a refractory pollutant) in water, graphene nanoparticles (GNPs) were successfully ...prepared by facile in situ pyrolysis method. Waste polyvinyl alcohol film was chosen as carbonaceous precursor in a “waste-to-treasure” strategy. By introducing boron (B) in the synthesis, the obtained B-doped GNPs (B-GNPs) exhibited more robust HCO performance. The ATZ degradation efficiencies by ozonation, GNPs, and B-GNPs catalytic ozonation after 10 min were 40.2 %, 69.8 %, and 83.2 %, respectively. In contrast to ozone activation in GNPs induced by oxygenated defects, boronated defects dominated ozone decomposition and subsequent reactive oxygen species generation (OH and O2–), imparting B-GNPs with greater activity and stability. Generally, B-doping promoted the electron transfer of B-GNPs, thus enhancing ozone adsorption and degradation. Also, the effect of various water matrices on ATZ degradation during HCO was comprehensively evaluated. Acute toxicity tests indicated rapid detoxification through deep ATZ degradation by B-GNP-catalyzed ozonation. This study provides a robust and efficient carbonaceous catalyst based on a “waste-treats-waste” strategy for environmental remediation, thereby providing insights into the mechanism and application of heteroatom-doped carbonaceous catalysts for the HCO process.
•GONs doping boosted the electrooxidation ability of Ti4O7 REM.•1wt% GONs doping significantly reduced the charge-transfer resistance.•The •OH yield of 1%GONs@Ti4O7 REM improves 2.5–2.8 times.•GONs ...doping can facilitate the stability of Ti4O7 REM.•Energy cost (EE/O) for treating 1,4-D was observed at only 0.34–0.74 kWh/m3.
Although Ti4O7 ceramic membrane has been recognized as one of the most promising anode materials for electrochemical advanced oxidation process (EAOP), it suffers from relatively low hydroxyl radical (•OH) production rate and high charge-transfer resistance that restricted its oxidation performance of organic pollutants. Herein, we reported an effective interface engineering strategy to develop a Ti4O7 reactive electrochemical membrane (REM) doped by graphene oxide nanoparticles (GONs), GONs@Ti4O7 REM, via strong GONs–O–Ti bonds. Results showed that 1% (wt%) GON doping on Ti4O7 REM significantly reduced the charge-transfer resistance from 73.87 to 8.42 Ω compared with the pristine Ti4O7 REM, and yielded •OH at 2.5–2.8 times higher rate. The 1,4-dioxane (1,4-D) oxidation rate in batch experiments by 1%GONs@Ti4O7 REM was 1.49×10−2 min−1, 2 times higher than that of the pristine Ti4O7 REM (7.51×10−3 min−1) and similar to that of BDD (1.79×10−2 min−1). The 1%GONs@Ti4O7 REM exhibited high stability after a polarization test of 90 h at 80 mA/cm2, and within 15 consecutive cycles, its oxidation performance was stable (95.1–99.2%) with about 1% of GONs lost on the REM. In addition, REM process can efficiently degrade refractory organic matters in the groundwater and landfill leachate, the total organic carbon was removed by 54.5% with a single-pass REM. A normalized electric energy consumption per log removal of 1,4-D (EE/O) was observed at only 0.2–0.6 kWh/m3. Our results suggested that chemical-bonded interface engineering strategy using GONs can facilitate the EAOP performance of Ti4O7 ceramic membrane with outstanding reactivity and stability.
Display omitted
•Adding graphene nanoparticles (GNPs) in PCM enhances its thermal conductivity.•Thermal conductivity of nano-PCM increased by 220% for 3 wt.% GNPs in the PCM.•Measured temperature dependant ...properties are expressed as UDF in ANSYS-Fluent.•The melting time reduction was about 36.5% for nano-PCM with 3 wt.% nano-graphene.•A higher mass fraction of graphene in PCM causes agglomeration and sedimentation.
Phase change materials (PCMs) low thermal conductivity limit the performance of latent heat thermal energy storage systems. To enhance the thermal conductivity of the heat storage medium, highly conductive additives could be added to the base PCM. Hence, the present work aims to perform numerical and experimental investigations on the melting heat transfer of the PCM (OM 65) loaded with highly conductive graphene nanoparticles (GNPs) at weight fractions of 1%, 2%, and 3%. Based on the aforementioned weight fractions of graphene nanoparticles in the PCM, the nanographene-enhanced PCM (NPCM) composites are named NPCM 1, NPCM 2, and NPCM 3 respectively. The temperature-dependant thermal conductivity and dynamic viscosity were measured. A transient heat transfer during the melting of the PCM and NPCMs in a two-dimensional rectangular domain heated from the bottom-up configuration was considered for the numerical study. The base temperature was maintained at a constant temperature (Th = 70 °C), and the remaining walls are adiabatic. The transient variation of liquid fraction and temperature were presented. The PCM and NPCMs are experimentally studied using the proposed three-dimensional rectangular test section with twenty-four thermocouples and a temperature logger. Compared to the base PCM, the reduction in melting time from the numerical and experimental study was 37.5% and 36.5% for NPCM 3. It was evident that adding GNPs to PCM enhances its thermal conductivity. However, the higher concentration of GNPs could drastically increase the NPCMs viscosity, as well as cause agglomeration and sedimentation of GNPs during melting. Therefore, adding a maximum of 3wt% GNPs into the PCM was recommended.
•Nanotechnology can be very helpful in developing thermal energy storage materials.•Thermal modeling of nano particle with phase change materials (PCM) is carried out.•These studies are crucial to ...enhance the thermal conductivity of PCM.•Graphene used as a nano particle, dispersed in CaCl2.6H2O, Capric acid and n-octadecane as PCM.
The thermal conductivity of commonly used phase change materials (PCM) for thermal energy storage (TES), such as, fatty acids, paraffin etc., is relatively poor, which is one of the main drawbacks for limiting their utility. In the recent past, few attempts have been made to enhance the thermal conductivity of PCM by mixing different additives in the appropriate amount. Graphene nanoparticles, having higher thermal conductivity may be a potential candidate for the same, when mixed appropriately with different PCM. In present study authors have carried out the numerical investigation for the melting of graphene nano-particles dispersed PCM filled in an aluminum square cavity heated from one side. In this work, the graphene nanoparticles are mixed in three different volumetric ratios (1%, 3%, and 5%), with three different commonly used categories of organic, inorganic and paraffin PCM (namely, Capric Acid, CaCl2·6H2O, and n-octadecane) to see the effect on melting of composite PCM developed. The resulting transient isotherms, velocity fields, and melting front and melt fractions thus have been deliberated in detail. These results clearly indicate that the addition of graphene nanoparticles increases melting rate but can also hamper the convection heat transfer within large cavities. The study also shows that such enhanced PCM can be effectively used for different TES applications in different fields. The prediction of temperature variation and rate of melting or solidification may be found useful especially for designing such TES devices.
Thermal conductivity of the Phase Change Materials (PCMs) of latent heat storage systems is enhanced by dispersing nanoparticles in base PCM for increased heat transfer rate. Heat transfer ...characteristics of the newly developed erythritol PCM dispersed with 1 wt% graphene nanoparticles in a newly designed shell and helical tube storage tank during charging and discharging processes was investigated. Both melting and solidification fronts progressed from the outer wall of the shell towards the axis on either side of the axis of the shell due to the helical tube arrangement. At the middle and near the axis of the storage tank, NDPCM melting time was decreased by 21% when inlet temperature of the hot therminol oil was increased from 160 °C to 180 °C and by about 30% when the oil flow rate was increased from 0.5 kg/min to 2 kg/min. Further, NDPCM solidification time was reduced by 11% when the cold therminol oil inlet temperature was decreased from 45 °C to 30 °C and by 20% when the oil flow rate was increased from 0.5 kg/min to 2 kg/min. Complete charging and discharging periods of NDPCM was reduced respectively by 20% at an inlet temperature of 180 °C and by 6% at an inlet temperature 30 °C for 1 kg/min flow rate of therminol oil compared with pure erythritol. This research study confirmed that the helical tube flow of heat transfer oil facilitated more uniform and quicker phase transition of PCM and graphene nanoparticles dispersed erythritol (NDPCM) had superior heat transfer behavior as compared to base erythritol and it can be utilized as a potential PCM for medium temperature thermal energy storage applications.
In this study, platinum nanochains (PtNCs), multi-walled carbon nanotubes (MWCNTs) and graphene nanoparticles (GNPs) were assembled together to form a novel nanocomposite by a facile ...ultrasonic-assisted blending process. The PtNCs-MWCNTs-GNPs nanocomposite was characterized by high resolution transmission electron microscopy (HR-TEM), energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The nanocomposite was used for the modification of glass carbon electrode (GCE) and simultaneous determination of dopamine (DA) and ascorbic acid (AA) by differential pulse voltammetry (DPV) and cycle voltammetry (CV). Under the optimum conditions, the calibration curves obtained are linear for the currents versus DA and AA concentrations over the range 2.00–50.0 μM and 100–1200 μM, respectively. And the detection limits for DA and AA are 0.500 μM and 10.0 μM, respectively. The detection and quantitative analysis of DA and AA in human serum and vitamin C tablets on PtNCs-MWCNTs-GNPs/GCE gave the recoveries of 104–110% and 101–108% with relative standard deviations (RSD) of 4.36–7.48% and 0.620–2.90%, respectively. The proposed PtNCs-MWCNTs-GNPs composite could provide a new platform for the routine analysis of DA and AA in terms of its good anti-interference ability, excellent reproducibility and repeatability, and feasibility of use.
•Fabrication and characterization of a novel PtNCs-GNPs-MWCNTs nanocomposite were performed.•The simultaneous determination of DA and AA at PtNCs-GNPs-MWCNTs/GCE was performed.•The anti-interference ability, repeatability and reproducibility of PtNCs-GNPs-MWCNTs/GCE were investigated.•The performances of PtNCs-GNPs-MWCNTs/GCE for DA and AA in actual samples were evaluated.
In recent times, materials with brilliant electromagnetic interference shielding (EMI) features captured the attention thanks to their applications in military, biological, and electronic apparatus. ...In this regard, hybrid polyvinyl alcohol/Graphene/Magnetite, PVA/Gr(x)/Fe3O4(0.1-x), nanocomposites were designed for the EMI shielding purposes. The obtained nanocomposites were characterized by various techniques like XRD, SEM, Raman, and FTIR. XRD patterns showed that the decrease in the crystallinity of the films with increasing the concentration of graphene (x) due to the decrease in the hydrogen bonding inside the nanocomposite. SEM images confirm the formation of graphene and Fe3O4 in the nano-scale with a fine dispersion in the matrix of PVA. The magnetite Fe3O4 nanoparticles show a high impact on the magnetization of the nanocomposites. The conductivity of the nanocomposite films increases with increasing the concentration of graphene (x) to be 0.32, 0.46, 0.9 and 1.87 S/cm for x = 0.02, 0.04, 0.06 and 0.08 wt%, respectively. The EMI shielding properties of the nanocomposite were performed in the X-band. The PVA/Gr/Fe3O4 nanocomposites display brilliant shielding effectiveness (SET) of 40.7 dB at 8 GHz with a very small amount of graphene x = 0.08 wt%, thanks to the synergetic effect of both graphene and magnetite nanoparticles and highest electrical conductivity of the nanocomposite. The main mechanism of shielding effectiveness is absorption. Finally, the synergetic effect, fine dispersion of nanoparticles, high magnetization, and high electrical conductivity are playing together to give this nanocomposite the advantage to be an excellent EMI shielding material.
Display omitted
•The nanocomposites PVA/Gr(x)/Fe3O4(0.1-x) have been prepared via the casting method for electromagnetic shielding.•The highest electrical conductivity of the PVA/Gr/Fe3O4 nanocomposite was 1.87 S/cm at graphene concentration x = 0.08 wt%.•The nanocomposites displayed EMI shielding effectiveness (SET) of 40.7 dB at very small amount of graphene x = 0.08 wt%.
PDF
